This is kind of a dumdum question, but whenever I go for extra long or extra fast rides, I notice that my stomach burns as though I've eaten a bunch of spicy food. It isn't painful, just odd. Am I feeling my fat burn off, or is it something else? Scale says I've lost another two pounds since posting this thread, so I'm inclined to think the former... but want to double-check just in case I'm hurting myself without realizing it.